NAME

       tracefs_instance_create, tracefs_instance_destroy, tracefs_instance_alloc, tracefs_instance_free,
       tracefs_instance_is_new, tracefs_instances, tracefs_instance_clear, tracefs_instance_reset - Manage trace
       instances.

SYNOPSIS

       #include <tracefs.h>

       struct tracefs_instance *tracefs_instance_create(const char *name);
       int tracefs_instance_destroy(struct tracefs_instance *instance);
       struct tracefs_instance *tracefs_instance_alloc(const char *tracing_dir, const char *name);
       void tracefs_instance_free(struct tracefs_instance *instance);
       bool tracefs_instance_is_new(struct tracefs_instance *instance);
       char **tracefs_instances(const char *regex);
       void tracefs_instance_clear(struct tracefs_instance *instance);
       void tracefs_instance_reset(struct tracefs_instance *instance);

DESCRIPTION

       This set of functions can be used to manage trace instances. A trace instance is a sub buffer used by the
       Linux tracing system. Given a unique name, the events enabled in an instance do not affect the main
       tracing system, nor other instances, as events enabled in the main tracing system or other instances do
       not affect the given instance.

       The tracefs_instance_create() function allocates and initializes a new tracefs_instance structure and
       returns it. If the instance with name does not yet exist in the system, it will be created. The name
       could be NULL, then the new tracefs_instance structure is initialized for the top instance. Note that the
       top instance cannot be created in the system, if it does not exist.

       The tracefs_instance_destroy() removes the instance from the system, but does not free the structure.
       tracefs_instance_free() must still be called on instance.

       The tracefs_instance_alloc()* function allocates a new tracefs_instance structure for existing trace
       instance. If the instance does not exist in the system, the function fails. The tracing_dir parameter
       points to the system trace directory. It can be NULL, then default system trace directory is used. This
       parameter is useful to allocate instances to trace directories, copied from another machine. The name is
       the name of the instance, or NULL for the top instance in the given tracing_dir.

       The tracefs_instance_free() function frees the tracefs_instance structure, without removing the trace
       instance from the system.

       The tracefs_instance_is_new() function checks if the given instance is newly created by
       tracefs_instance_create(), or it has been in the system before that.

       The tracefs_instances() function returns a list of instances that exist in the system that match the
       regular expression regex. If regex is NULL, then it will match all instances that exist. The returned
       list must be freed with tracefs_list_free(3). Note, if no instances are found an empty list is returned
       and that too needs to be free with tracefs_list_free(3).

       The tracefs_instance_clear() function clears the ring buffer of the given instance or the top level ring
       buffer if instance is NULL.

       The tracefs_instance_reset() function resets the given instance to its default state.

RETURN VALUE

       The tracefs_instance_create() and tracefs_instance_alloc() functions return a pointer to a newly
       allocated tracefs_instance structure. It must be freed with tracefs_instance_free().

       The tracefs_instance_destroy() function returns 0 if it succeeds to remove the instance, otherwise it
       returns -1 if the instance does not exist or it fails to remove it.

       The tracefs_instance_is_new() function returns true if the tracefs_instance_create() that allocated
       instance also created the trace instance in the system, or false if the trace instance already existed in
       the system when instance was allocated by tracefs_instance_create() or tracefs_instance_alloc().

       The tracefs_instances() returns a list of instance names that exist on the system. The list must be freed
       with tracefs_list_free(3). An empty list is returned if no instance exists that matches regex, and this
       needs to be freed with tracefs_list_free(3) as well. NULL is returned on error.

       The tracefs_instance_clear() returns 0 if it successfully cleared the ring buffer, or -1 on error.

EXAMPLE

           #include <tracefs.h>

           struct tracefs_instance *inst = tracefs_instance_create("foo");
                   if (!inst) {
                           /* Error creating a new trace instance */
                           ...
                   }

                   ...

                   if (tracefs_instance_is_new(inst))
                           tracefs_instance_destroy(inst);
                   tracefs_instance_free(inst);
           ...

           struct tracefs_instance *inst = tracefs_instance_alloc(NULL, "bar");
                   if (!inst) {
                           /* Error allocating 'bar' trace instance */
                           ...
                   }

                   ...
                   tracefs_instance_reset(inst);
                   tracefs_instance_free(inst);

FILES

           tracefs.h
                   Header file to include in order to have access to the library APIs.
           -ltracefs
                   Linker switch to add when building a program that uses the library.

SEE ALSO

       libtracefs(3), libtraceevent(3), trace-cmd(1)

AUTHOR

           Steven Rostedt <rostedt@goodmis.org[1]>
           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>

REPORTING BUGS

       Report bugs to <linux-trace-devel@vger.kernel.org[3]>

LICENSE

       libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES

       https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

COPYING

       Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public
       License (GPL).

NOTES

        1. rostedt@goodmis.org
           mailto:rostedt@goodmis.org

        2. tz.stoyanov@gmail.com
           mailto:tz.stoyanov@gmail.com

        3. linux-trace-devel@vger.kernel.org
           mailto:linux-trace-devel@vger.kernel.org